Roll fusing device for xerographic material



w. A. STRYJEWSKI 3,452,181

June 24, 1969 ROLL FUSING DEVICE FOR XEROGRAPHIC MATERIAL Sheet FiledDec.

:55 n6 wuqmmaw E qmlmmq QSQI m mwbte AGENT un 24,1 6 W.A.STRYJEWSK| 3,4581 ROLL FUSING DEVICE FOR XEROGRAPHIC MATERIAL Filed Dec. 2'7, 1967Sheet ,3 of 2 FIG 2 WALTER A. STRYJEWSK/ INVENTOR.

@z V M AGENT 3,452,181 Patented June 24, 1969 US. Cl. 219-216 14 ClaimsABSTRACT OF THE DISCLOSURE A device for fusing an electroscopic tonerimage to the surface of a carrier bearing the image in which the carrieris moved through a fusing station by a thermally transparent drum and aresilient roll that are synchronously driven. A heating element and areflector are mounted within the drum, the reflector focusing the heatgenerated by the heating element into a line lying in a plane generallycorresponding to the image bearing surface of the carrier and upstreamfrom the line of contact of the drum and roll relative to the directionof movement of the carrier. The toner image is heated sufliciently to atleast partially tackify the toner particles prior to engagement thereofby the drum for fusing to the carrier. A second heating element can bedispersed in close proximity to the carrier to preheat the toner imageat a location upstream from the focused line of heat, thereby permittingthe linear speed of the carrier to be increased.

Field of the invention The present invention relates to fusing anelectroscopic toner image to the surface of a carrier bearing said tonerimage and more particularly to a device in which the toner image isheated to an extent suflicient to fuse it to the carrier just prior toits entry into the nip of a pair of rotating members.

Description of the prior art It is well known to fuse toner particles toa carrier by means of heated rolls, or by the application of heatdirectly to the toner particles by means of hot vapors, etc. Inapparatus utilizing any one of the aforementioned types of fusing, hightemperatures are required to obtain satisfactory fusing of the tonerparticles to the carrier. With the use of one or a pair of heated rollsfor fusing toner images, a heating element is usually arranged withineach of the rolls which are usually constructed of a highly conductiveand heat-absorbing material, such as copper, steel or aluminum. In thiscase, the softening of the toner particles and fusing of the tonerparticles to the carrier occur practically simultaneously, that is, atthe time of contact of the carrier and toner image with the heatedrolls. If the rate of movement of the carrier is relatively slow inorder to accomplish good fusing, the heat penetration can causediscoloration of the carrier.

Summary of the invention One object of the invention is to provide adevice for fusing electroscopic toner images to the surface of a carrierbearing said image in which the carrier can be moved at a relativelyhigh speed to eliminate any possibility of discoloring or charring ofthe carrier due to excessive heat.

Another object of the invention is to provide a device for fusingxerographic images to a carrier in which the toner particles aresoftened to an extent sufficient to cause fusing to the carrier prior toentry of such particles into contact with a pair of rolls.

And yet another object of the invention is to provide a device forfusing xerographically toned images in which an eflicient transfer ofheat to only the toned image and the upper surface of the carrier towhich it is to be fused is obtained.

These and other objects of the invention will be apparent to thoseskilled in the art when the following description is read in conjunctionwith the disclosure of the invention shown in the accompanying drawings.

The aforementioned objects of the invention are at tained by a fusingdevice comprising a rotatable, cylindrical drum which is made of athermally transparent material having high radiation transmittingqualities. A resilient reflecting and heat insulating surfaced roll ismounted to cooperate with the surface of the drum for moving the carrierbearing the toner image or images therebetween. The drum and roll arerotated in synchronism by a suitable drive mechanism. An elongatedheating element is mounted within the drum and is partially surroundedby an elongated elliptical reflector. The reflector is of such a designthat one of its principal focal lines is coincident with the axis of theheating element and the other focal line is generally coincident withthe surface of the carrier bearing the toner image along a line lyingoutside the drum. The reflector is so positioned that the heat generatedby the heating element is focused onto the surface of the carrier justahead of the line of contact of the drum and roll in an upstreamdirection relative to the direction of movement of the carrier. Withthis arrangement, the toner image is heated sufliciently to at leastsoften the toner particles to such an extent that they are at leastpartially fused to the carrier prior to engagement thereof by the drum.

In one of the modifications of the aforementioned device, an auxiliaryheating element can be mounted outside of the drum in close proximity tothe surface of the carrier in an upstream direction relative to thedirection of movement of the carrier for preheating the toner particles,thereby permitting the carrier to be moved at a much faster rate toaccomplish the fusing operation, The roll contacting the drum can bemounted so as to be moved into cooperative relationship with the drumonly when the carrier is to be moved therebetween, such movement beingcontrolled by a switch that is actuated by the leading edge of thecarrier. The peripheral surface of the drum can be treated or coated soas to provide a transparent nonoffsetting surface which will preventtoner particles from transferring from the carrier to the surface of thedrum and then being offset onto undesired areas of the carrier.

Description of the drawings Reference is now made to the accompanyingdrawings wherein like reference numerals designate like parts andwherein:

FIG. 1 is a vertical section through the apparatus embodying theinvention and showing the principal elements of the fusing device;

FIG. 2 is a vertical section through one end of the fusing deviceshowing the mounting arrangement for the drum, heating element and roll;and

FIG. 3 is a simple schematic wiring diagram showing the principalelectrical elements associated with the fusing device.

Description 0 the preferred embodiment With reference to FIG. 1 acarrier 10 comprises a material, such as paper, on one surface S ofwhich toner particles in an image formation are lightly held by a slighttriboelectric effect. The carrier 10 can be positioned manually or bysuitable driving means relative to a drum 11 and a roll 12. The carrier10 must be pOsitioned so that the toner image on surface S faces thedrum 11. As will be described in more detail hereinafter, drum 11 androll 12 serve to move the carrier therebetween.

As shown in FIG. 2, the drum 11 comprises a glass or quartz sleeve 13having high thermal radiation transmitting qualities that is engaged oneach end by a flanged disc 14 rotatably supported by a pair of spacedbearings 15. Each pair of bearings 15 is carried by an arbor 16 that ismounted in one of the spaced supports 17 which can be a part of a framefor the fusing device. One of the flanged discs 14 is provided with anintegral pulley portion 18 which is connected by a belt 19 eitherdirectly or through a suitable drive mechanism to a motor 20. One disc14 also includes a flange 21 having gear teeth 22 formed integraltherewith.

Again referring to FIG. 2, roll 12 comprises a metallic core 23 to whicha resilient sleeve 24 is firmly attached or adhered. The sleeve 24 ismade preferably of silicone rubber covered with a heat reflectingmaterial 25, such as foil of stainless steel, which in turn is coveredwith a heat insulating material 26, so as to withstand relatively hightemperatures and not absorb heat from the carrier 10. One end of roll 12carries a gear 27 which is continuously in mesh with gear 22 on drum 11.Roll 12 is normally maintained in a position in which it is disengagedfrom the drum, but in which position gears 22 and 27 are still engagedto provide continuous rotation of drum 11 and roll 12. Roll 12 isrotatably mounted between a pair of spaced levers 28, each of which ispivotally mounted on one of the supports 17 by means of a stud 29. Oneof the levers 28, as shown in FIG. 1, is provided with an arm 30, thefree end 31 of which is pivotally connected to the armature 32 of asolenoid 33. A spring 34 having one end connected to extension normallyholds the roll 12 in a position in which it is disengaged from drum 11in which position one of the levers 28 engages a movement limiting pin35.

Roll 12 is moved into cooperative relationship with drum 11 by solenoid33 which is controlled by means of a switch 36 which has two sets ofcontacts 36A and 36B and is arranged in the path of movement of thecarrier 10. As the carrier 10 is moved toward the drum 11, the leadingedge thereof actuates switch 36 to a closed position, whereby solenoid33 is energized and roll 12 is moved toward drum 11. Solenoid 33 ismaintained in an energized state so long as the carrier 10 holds switch36 closed and can be provided with a conventional delay or holdingcircuit so that roll 12 is held in cooperative relationship with drum 11until the trailing edge of the carrier has been moved past the line ofcontact of drum 11 and roll 12. This biasing arrangement of roll 12allows it to be moved or displaced slightly relative to drum 11 when acarrier 10 is moved therebetween to accommodate for the thickness of thecarrier. When roll 12 is moved toward drum 11, gears 22 and 27 becomefully engaged and the movement of drum 11 and roll 12 is then insynchronism so that an even and uniform movement of carrier 10 isobtained. The drum 11 and roll 12 could also be driven in synchronism bya belt system or other drive means which will permit one to be movedrelative to the other when a carrier is presented for fusing and at thesame time provide continuous movement of both the drum and roll.

An elongated heating element 40 is mounted within drum 11 and betweenthe side walls 41 of an elongated elliptical reflector 42. The sidewalls 41 are secured to the arbor 16 by means of screws 43 as shown inFIG. 2. The axis of heating element 40 can be coincident with the axisof drum 11 or positioned relative to the axis of the drum but stillparallel thereto. The heating element 40 is preferably a tungstenfilament lamp although any other type of radiant heat generator can beused.

The reflecting means 42 comprises an elongated, elliptical surface 44which is of high reflectance or plated and polished to provide a highdegree of reflectance. The focal lines of the elliptical reflector aresuch that one lies within the drum and the other outside the drum, bothlines being generally parallel to each other, to the axis of drum 11 andto the axis of heating element 40. The focal line F1 which is within thedrum, is preferably coincident with the axis of the heating element 40and the focal line F2, which is outside the drum, is preferablycoincident with a plane generally corresponding to the plane of theimage bearing surface S of the carirer 10. It is a well known principlethat such a reflector will focus the radiation generated by the heatingelement 40 from the focal line F1 as a relatively narrow band to thefocal line F2 which lies outside of the drum 11. With such a reflector,practically all of the heat is therefore focused as a narrow band in theplane of the image surface S and transverse to the direction of movementof the carrier 10. It has been found that the focal line F2 should belocated upstream from the line of tangency or contact of drum 11 androll 12 relative to the direction of movement of carrier 10. The focallines F1 and F2, which are parallel to each other, determine the majoraxial plane of the reflector 40, the axial plane being angularlydisposed relative to focal line F1 in a direction opposed to thedirection of movement of carrier 10. With reference to FIG. 1, suchplane would be normal to the plane of the drawing and pass through thepoints representing focal lines F1 and F2. The distance between the lineof contact of drum 11 and roll 12 and focal line F2 can be approximatelyone-quarter inch. With such a separation between the line of heating andthe line of contact, the carrier 10 can be moved at a relatively highlinear speed and accomplish good fusing of the toner particles to thecarrier, the speed be ing dependent on various parameters, such as thetype of toner, the heat generated by the heating element 40, etc. Theheating of the toner particles on the carrier 10 prior to engagement bydrum 11 softens the toner particles sufficiently to provide good fusingto the carrier when contacted by the drum. Since the roll 12 is urgedtoward drum 11, the pressure exerted by roll 12 also aids in obtaininggood fusing of the toner particles.

It has been found that higher linear speeds of the carrier 10 can beattained with good fusing of the toner particles to the carrier when thetoner particles are also subjected to the heat generated by an auxiliaryheating element prior to that generated by the heating element 40. Asshown in FIG. 1, an auxiliary heating element 46 is mounted upstreamfrom the focal line F2 and in the nip between drum 11 and carrier 10.The heating element 46 can be partially surrounded by an elongatedreflector 47 so that the heat is directed to the surface of carrier 10.The heating element 46 must be of necessity relatively small andpositioned sufliciently far into the nip between drum 11 and carrier 10in order that the toner particles do not again harden before coming intocontact with the line of heat at focal line F2. While heating element 46has been shown as a tubular lamp, the same results can be obtained bymeans of a heating wire or similar device which will permit the elementto be moved still further into the designated nip. A reflector 48 ispositioned below the plane of movement of carrier 10, see FIG. 1, toreflect any heat transmitted through the carrier and to reflect the heatat focal line F2 and/or from the heating element 46, when a carrier 10is not present, thereby shielding any part of the mechanism therebelow.

As mentioned hereinabove, toner particles will tend to transfer from thecarrier to the surface of a heated roll or drum with offsetting of theseparticles onto the carrier in desired areas relative to another part ofthe same image or on another image. It has been found that coating orplacing a sleeve of a transparent offset-preventing ma terial on theperipheral surface of drum 11 serves to eliminate such migration ortransfer of the toner particles. This migration can be further reducedby applying an offset-preventing liquid to the offset-preventingmaterial on the surface of drum 11. It is known that a material, such astetrafiuoroethylene polymer (Teflon) can be applied to the surface ofdrum '11, either as a coating or as a sleeve, and in combination withsilicone oil will serve to prevent such migration of the tonerparticles. Applicant has found that coating the peripheral surface ofdrum 11 with silicone varnish and applying silicone oil to the coatedsurface also provides a combination of material and liquid which willeffectively prevent toner migration. As shown in FIG. 1, the siliconevarnish layer is designated by the numeral 50 and the offset-preventingliquid, such as silicone oil, is contained in a well 51 and applied toand across the width of the silicone varnish layer on drum 11 by meansof a wick 52. Flurocarbon surfactants can also be applied to theperipheral surface of drum L1 to prevent migration of the tonerparticles. One of the prime requisites of the offset-preventing materialand liquid is that both must be good transmitters of radiation and,secondly, that no chemical reaction occurs in the range of temperaturesnecessary for fusing the toner particles. Both silicone varnish andsilicone oil meet these requirements. Applicant has also found that aflurocarbon monomer can be used as a transparent layer on drum 11 toprevent toner migration and that hydrogenated vegetable oil andglyceride can be used as an offset-preventing liquid.

In using the fusing device described hereinabove, switch 55 is firstclosed to energize motor 20, thereby rotating drum 11 and roll 12through gears 22 and 27, and heating elements 40 and 46, the latterelements being controlled by a thermostatic control T which limits theheat to be generated to a standby requisite. When a carrier to be fusedis moved toward the drum, the leading edge first engages the switch 36,thereby closing its contacts 36A and 36B. The solenoid 33 is thenenergized (contact 36A) and moves roll 12 into cooperative relationshipwith drum 11 so that both are rotating in synchronism prior to engagingthe carrier 10. Thermostatic control T is shorted out (contact 36B) toprovide heating elements 40- and 46 with full line voltage to providethe necessary heat output for fusing. As the carrier moves toward thefusing station, the toner particles are first heated by element 46 andthen by the heat generated by heating element 40' and focused thereon byreflector 42, so that by the time the toner particles are engaged bydrum 11, they are tackified to the extent that they need only besqueezed together and pressed into the surface of carrier by drum 111and roll 12 to complete the fusing operation. It will be obvious tothose skilled in the art that because of the heat applied to the tonerparticles prior to engagement by drum 11, the temperature of thetransparent sleeve 13 need not be as high as would normally be requiredif only the drum 11 were accomplishing the complete fusing of the tonerimage. The distance between the line of contact of drum 11 and roll12and the focal line F2 of reflector 42 can be varied to provide optimumfusing in accordance with the rate of movement of the carrier 10, forexample, with a distance of about one-quarter inch between the line ofcontact of drum 11 and roll 12 and the focal line F2, the linear speedof carrier 10 can be about 10 inches per second.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

I claim:

1. A device for fusing an electroscopic toner image to the surface of acarrier bearing said toner image, comprising:

a rotatable, substantially thermally-transparent drum;

a movable member for engaging said carrier in cooperation with said drumalong a line of contact generally parallel to the axis of said drum andfor moving said carrier along a predetermined path therebetween with theimage bearing surface of said carrier facing said drum;

means for moving said drum and member in synchronism;

a heating element mounted within said drum; and

means arranged relative to said heating element and within said drum forfocusing the heat generated by said heating element through said drumand substantially into a line lying in a plane generally correspondingto the plane of movement of the image bearing surface along said path,said line of focused heat being disposed generally parallel to said lineof contact and upstream therefrom relative to the direction of movementof said carrier;

whereby said toner image is heated sufficiently to at least partiallytackify the toner particles prior to engagement thereof by said drum forfusing to said carrier.

2. A fusing device in accordance with claim 1 wherein said movablemember comprises a roll having a heat reflecting medium in closeproximity to said drum.

3. A fusing device in accordance with claim 1 wherein said heatingelement is elongated and said focusing means comprises an elongated,elliptical surface having one focal line generally coincident with theaxis of said heating element and the other focal line lying outside ofsaid drum and generally coincident with the plane Otf movement of saidimage bearing surface.

4. A fusing device in accordance with claim 1 wherein said heatingelement is elongated and said focusing means comprises an elongated,elliptical surface having the major axial plane thereof disposedangularly about the axis of said heating element in a direction opposedto the direction of movement of said carrier, one focal line of saidelliptical surface being within said drum and generally coincident withthe axis of said heating element and the other focal line lying outsideof said drum and generally coincident with the plane of movement of saidimage bearing surface.

5. A fusing device in accordance with claim '1 including a secondheating element disposed in close proximity to the plane of movement ofthe image bearing surace of said carrier and positioned to preheat saidtoner image at a location upstream relative to the direction of movementof said carrier from the location at which said line of heat is focusedon said image bearing surface by said reflector means.

6. A device for fusing an electroscopic toner image to the surface of acarrier bearing said toner image, comprising:

a rotatable, substantially thermally-transparent drum having asubstantially thermally-transparent layer of offset-preventing materialon its peripheral surface;

a rotatable, resilient roll for engaging said carrier in cooperationwith said drum along a line of contact generally parallel to the axis ofsaid drum and for moving said carrier along a predetermined paththerebetween with the image bearing surface facing said drum;

means for rotating said drum and said roll in synchronrsm;

an elongated, radiant heating element mounted within said drum with itsaxis generally parallel to the axis of said drum;-

reflector means arranged relative to said heating element and withinsaid drum for focusing the heat [generated by said heating elementthrough said drum and substantially into a line lying in a planegenerally corresponding to the plane of movement of the image bearingsurface of said carrier along said path, said line of focused heat beingdisposed generally parallel to said line of contact and upstreamtherefrom relative to the direction of movement of said carrier;

whereby said toner image is heated sufi'iciently to at least partiallytackify the toner particles prior to engagement thereof with said drumfor fusing to said carrier.

7. A fusing device in accordance with claim 6 including means forapplying an offset-preventing liquid to the offset preventing materialon said drum.

8. A fusing device in accordance with claim 7 wherein said transparentlayer is a tetrafiuroethylene polymer and said said offset-preventingliquid is a silicone oil.

9. A fusing device in accordance with claim 7 wherein said transparentlayer consists of one of a tetrafluroethylene polymer, a siliconevarnish and a fiurocarbon monomer, and said offsetting liquid consistsof one of silicone oil, a hydrogenated vegetable oil and a glyceride.

10. A fusing device in accordance with claim 6 including a secondheating element disposed in close proximity to the plane of movement ofthe image bearing surface of said carrier and positioned to preheat saidtoner image at a location upstream relative to the direction of movementof said carrier from the location at which said line of heat focused onsaid image bearing surface by said reflector means.

11. A device for fusing an electroscopic toner image to the surface of acarrier bearing said toner image, comprising:

a rotatable, substantially thermally-transparent drum having a layer ofsubstantially thermally-transparent oifset-preventing material on itsperipheral surface;

a rotatable, resilient roll movable between a first position in which itis disengaged from said drum and a second position in which it contactssaid drum along a line generally parallel to the axis of said drum, saidroll being displaceable from said drum when said carrier is movedtherebetween for moving the latter along a predetermined path with theimage bearing surface of said carrier facing said drum;

means responsive to actuation by the leading edge of said carrier formoving said roll from said first position toward said second position;

an elongated, radiant heating element mounted within said drum with itsaxis generally parallel to the axis of said drum; and

reflector means arranged relative to said heating element and withinsaid drum for focusing the heat generated by said heating elementthrough said drum 8' and substantially into a line lying in a planegenerally corresponding to the plane of movement of the image bearingsurface along said path, said line of focused heat being disposedgenerally parallel to said line of contact and upstream therefromrelative to the direction of movement of said carrier; whereby saidtoner image is heated sufiiciently to at least partially tackify thetoner particles prior to engagement thereof with said drum for fusing tosaid carrier.

12. A fusing device in accordance with claim 11 including means forapplying an offset-preventing liquid to said layer of offset-preventingmaterial on the peripheral surface of said drum.

13. A fusing device in accordance with claim 11 wherein said reflectormeans comprises an elongated, generally semi-elliptical surface havingone focal line generally coincident with the axis of said heatingelement and the other focal line lying outside of said drum andgenerally coincident with the plane of movement of said image bearingsurface.

14. A fusing device in accordance with claim 11 including a secondelongated heating element disposed in close proximity to the plane ofmovement of the image bearing surface of said carrier and positioned topreheat said toner image at a location upstream relative to thedirection of movement of said carrier from the location at which saidline of heat is focused on said image 30 bearing surface by saidreflector means.

References Cited UNITED STATES PATENTS RICHARD M. WOOD, PrimaryExaminer.

P. W. GOWDEY, Assistant Examiner.

US. Cl. X.R.

